Abstract Background Premature ovarian failure which leads to loss of fertility and low level of estrogen have serlously affected women's physical and mental health, especially, women of child-bearing age. The etiology remains unclear. DNA methylation, as a key epigenetic modification might play an importan role in primary ovarian insufficiency (POI). We explore the whole DNA methylation of POI by whole genome bisulfite sequencing (WGBS), and find the pattern of DNA methylation in POI and analyze the differentially methylated regions (DMRs) genes related POI. Methods According to clinical and experimental standards, follicular fluid samples were collected from three women with POI and three women with normal ovarian reserve (NOR). Ovarian granulosa cells were purified from each follicular fluid sample. Whole genomic DNA methylation sequencing of the granulosa cells was performed by WGBS. Results We obtained whole-genome methylation maps of human granulosa cells. The average percentages of methylated cytosines in CG contexts exceeded 99%, in CHG and CHH contexts was less than 1%. The average methylation level in CG was about 80%, in CHG and CHH was less than 0.4%. there was no significant difference in CpG methylation level between NOR and POI. But there were DMRs between two groups. Distribution of DMRs was enriched in promoter and exon. Differentially methylated genes were used to perform Gene ontology(GO) analysis and enriched in GO items of cellular process, biological regulation, metabolic process, developmental process,binding and catalytic activities. Conclusion DNA methylation plays a critical role in POI and serve as resources for further investigation in the future.

Premature ovarian insufficiency (POI) is a disorder of ovarian function, which occurs in approximately 3.7% of women younger than 40 years of age.1 The aetiologies of most cases were unknown and usually manifest as isolated organ senescence at early stage of diagnosis, only with long-term consequences of increased risk of metabolic syndrome or disease.2 We tried to explore the essence of POI from multiple dimensions. First, we found that upregulated genes in POI patients’ ovarian granulosa cells were mainly enriched in metabolic pathways. Then, we profiled metabolites in the patients’ sera and identified some metabolites with changed levels, including fumarate, arachidonate and acetoacetate, and the combination of hyodeoxycholic acid (HDCA) and acetoacetate may be used as one of potential biomarkers for POI. In addition, we found genes with upregulated transcription levels and differential methylated levels were enriched in oxidative stress pathways, which can be also elucidated from abnormal metabolism.The transcriptomes of patient and control granulosa cells were profiled, and 3966 differentially expressed genes (DEGs) (fold change > 2, Padj < .05) were identified (Table S1). Gene ontology analyses found that downregulated DEGs were mainly related to extracellular matrix/structure organization and different types of junctions. The upregulated DEGs were enriched in various catabolic/metabolic/biosynthetic/processes (Figure 1A). KEGG (Kyoto Encyclopaedia of Genes and Genomes) analysis showed that cytokine–cytokine receptor interaction, PI3K-Akt-signalling pathway and MAPK-signalling pathway were enriched in the downregulated genes, whereas the metabolic pathway was the most enriched in the upregulated genes. Moreover, other pathways, such as amino acid degradation, synthesis, peroxisome and oxidative phosphorylation, were also enriched in upregulated DEGs (Figure 1B). Several previous studies present valuable information about metabolic features of POI, which mainly focus on total cholesterol, lipoprotein cholesterol and glucose metabolism.3-6 Elevated levels of free fatty acids in follicular fluid were also reported as a potential driver of human POI.7 However, many of these results were inconsistent and not so comprehensive, although they have been noteworthy. Therefore, we carried out metabolomic analyses on serum samples from POI patients and controls. The outlined demographic characteristics of all recruited patients and controls were shown (Table 1). Two cohorts were enrolled in the metabolomic analyses in this study (Figure 2A). In the discovery cohort, a total of 6 categories of 181 features were reliably detected. POI patients could be clearly distinguished from controls by conducting multivariate statistical analysis (Figure 2B). Sixty-two features with VIP (variable importance in projection) values greater than 1 were identified and considered as differential metabolites (DMets). Subsequently, 26 of the 63 DMets were found to be significantly different between POI patients and controls using univariate t test analysis (p < .05) (Figure 2C; Table S2). Next, 32 out of the 62 features were validated using the validation cohort (Table S3). The numbers of metabolites in the union and intersections of the DMets identified from the discovery and validation cohorts were 39 and 13, respectively. Pearson's correlation coefficient figure and heat map analysis of the 39 DMets are shown (Figure S1). Enrichment and pathway analysis of the 39 DMets are shown respectively (Figure 2D,E). Out of the 13 validated DMets, 5 (acetoacetate, glutamate, C22:1, arachidonate and succinate) and 4 (HDCA, C22:0, homocitrulline [Hcit] and fumarate) were increased and decreased in the sera of POI patients, respectively. In addition, ROS and LDH (lactic dehydrogenase) were increased, and NADH and ATP were decreased in patients (Figure 2F). Receiver-operating characteristic (ROC) analysis was performed and 8 metabolites had area under curve (AUCs) greater than .7. In addition, the top two combinations with the highest AUCs were NADH plus acetoacetate (.868) and HDCA plus acetoacetate (.955) (Figure 2G,H). Furthermore, we reanalysed the human granulosa cell whole-genome DNA methylation profiling data that we previously generated.7 A number of 536 genes were hypermethylated in their differentially methylated regions (DMRs), whereas 1583 genes with hypomethylated DMRs were identified (Table S4; Figure S2). Integrating our transcriptomic and methylomic data, we found that 240 differentially expressed and methylated genes (DEMGs) were mainly enriched in response to oxidative stress, response to chemical stress, reactive oxygen species and hydrogen peroxide (Table S5; Figure S3A,B). DNMT3, DNMT1, methylenetetrahydrofolate reductase) and 5-methyltetrahydrofolate–homocysteine methyltransferase reductase, involved in methionine cycle, were differently expressed in POI patients’ granulosa cells (Figure S3C). We next conducted network analysis on these DEMGs and the metabolites we detected (Table S6; Figure S4). The top five DMets were ATP, arachidonate, serotonin, glutamate and citrate. Glutamine synthetase (GLUL) and FOS were revealed as the top two hub genes in terms of connectivity with metabolites. GLUL, which catalyses the ATP-dependent conversion of glutamate and ammonia to glutamine, is related to 9 metabolites and was significantly upregulated and hypomethylated in exonic regions and the 3′UTRs. In-line with this, metabolic profiling showed decreased ATP and increased glutamate in POI patients. FOS was related to 8 metabolites and significantly upregulated and hypomethylated in exonic and 3′UTR regions (Figure 3A). It was also recently reported as a hub gene in the gene regulatory network of antioxidant in aged monkeys and human ovaries.8 In addition, we searched the human metabolome database for the associated enzymes/proteins of the 39 DMets. Changes in the expression and methylation status of these genes were displayed using Cytoscape software (Table S7; Figure S4). Joint-pathway analysis of DEMGs and DMets showed pathways those were impacted (Figure 3B). All the previous analyses were summarized as a metabolic network composed of DMets and enzymes of DEMGs that may contribute to the aetiology of POI (Figure 3C). Genes for NMNAT, PAR3 and NAMPT, enzymes involved in the synthesis or consumption of nicotinamide adenine dinucleotide (NAD+), which were reported associated with POI or ovarian ageing,9, 10 were upregulated or downregulated DEGs. In summary, the integrated analyses of transcriptomic and methylomic data from granulosa cells of the human ovary and the metabolomic data from human sera have identified increased levels of acetoacetate and arachidonate and disturbances in the TCA (tricarboxylic acid) cycle, fatty acids, ketone bodies and antioxidative processes, all of which contribute to decreased levels of NADH and ATP, increased oxidative stress and eventually ovarian premature senescence. Our data not only yielded valuable fundamental insights into its pathological mechanism but also would aid in the development of new therapeutic targets for POI. The causal effect relationship between gene expression and metabolic changes warrants further investigation in the future. This work was supported by the National Natural Science Foundation of China (81971349 and 81300456 to Cuiling Lu) and National Key Research and Development Program of China (2018YFE0201100 to Chunsheng Han and 2016YFC1000302 to Xiumei Zhen). The authors declare that there is no conflict of interest. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

STUDY QUESTION Could in vitro maturation (IVM) following transvaginal oocyte retrieval during gynaecological surgery (IVM-surgery) be an effective and safe strategy for fertility preservation? SUMMARY ANSWER IVM-surgery on unstimulated ovaries is a novel option that can be considered for fertility preservation for women requiring gynaecological surgery, but more research is needed to identify appropriate patients who may benefit and to determine the cost-effectiveness of such an approach. WHAT IS KNOWN ALREADY IVM followed by oocyte/embryo cryopreservation has been useful as a safe reproductive strategy for some infertile women. STUDY DESIGN, SIZE, DURATION This prospective cohort study comprised 158 consecutive women with polycystic ovary syndrome (PCOS) who underwent laparoscopy or hysteroscopy for other reasons and had concomitant transvaginal oocyte retrieval followed by IVM between 2014 and 2016. PARTICIPANTS/MATERIALS, SETTING, METHODS A total of 158 women with anovulatory PCOS who underwent IVM-surgery in our infertility centre were recruited for this study. Matured IVM oocytes obtained from these women were either freshly fertilized and subsequently frozen at the blastocyst stage (fresh oocyte group, n = 46) or the oocytes were frozen (frozen oocyte group, n = 112) for fertility preservation followed by later thawing for insemination and cleavage embryo transfer (ET) (n = 33). The following outcomes were then evaluated: embryological data, clinical pregnancy rate, live birth rate (LBR), neonatal outcomes, post-operative complications and post-operative ovarian function. MAIN RESULTS AND THE ROLE OF CHANCE Among all the women who underwent IVM-surgery, the clinical pregnancy rate and LBR per initiated IVM cycle were 9.5% (15/158) and 6.9% (11/158), respectively. Women (40.6%, 20/33) who underwent the procedure with frozen-thawed oocytes (oocyte survival rate, 83.0%) obtained a high quality of cleaved embryos. In the fresh oocyte group, the clinical pregnancy rate and LBR per ET cycle were 69.2 and 53.8%, respectively. In the frozen oocyte group, the clinical pregnancy rate and LBR per ET cycle were 28.6 and 19.1%, respectively. No adverse neonatal outcomes were recorded. IVM-surgery was not associated with post-operative complications, a longer hospital stay, or impaired ovarian function. LIMITATIONS, REASONS FOR CAUTION Because of the small sample size and the low utilization rate and cost-effectiveness per retrieval, the present findings should be interpreted with caution, and further studies are needed for the long-term follow-up of live births. WIDER IMPLICATIONS OF THE FINDINGS This strategy can also help patients with normal ovulation to obtain available oocytes and embryos for cryopreservation and subsequent use. STUDY FUNDING/COMPETING INTEREST(S) This research was supported by the Joint Research Fund for Overseas Natural Science of China (No. 31429004), the National Key Research and Development Program of China (No. 2017YFC1002000, 2017YFC1001504, 2016YFC1000302), the Ministry of Science and Technology of China Grants (No. 2014CB943203), the Chinese Society of Reproductive Medicine Fund (No. 16020400656) and the National Natural Science Foundation of China (No. 81300456). All the authors have nothing to disclose in terms of conflicts of interest. TRIAL REGISTRATION NUMBER chictr-ONC-17011861.

Table S6. Pathway enrichment of genes down-regulated in the Gns group compared with the Control group. (XLSX 26 kb)

Superovulation treatment had some adverse effects on maturity and development of oocytes. Can superovulation dose of gonadotropins (Gns) affect the transcriptome of granulosa cells and follicular fluid (FF) hormone levels? One leading pre-ovulatory follicle per subject was used from three natural-cycle and four Gn-stimulated patients. Granulosa cells and FF samples were collected from the same leading follicle of each patient. RNA was extracted from granulosa cells and subjected to deep sequencing and analysis. Follicle-stimulating hormone (FSH), estradiol (E2), androstenedione (AND), testosterone (T), luteinizing hormone (LH), and progesterone (P4) levels in FF were measured by immunoassays. Student’s t test was used for statistical analysis. A total of 715 genes were up-regulated, and 287 genes were down-regulated, in the Gn-stimulated group relative to the control group. Gene Ontology analysis revealed that the down-regulated genes were enriched in cell cycle and meiosis pathways, primarily those associated with follicle or oocyte maturation and quality. On the other hand, the up-regulated genes were enriched in functions related to immunity and cytokine–cytokine receptor interactions. Compared to the follicles of natural cycle, the E2 and LH concentrations were significantly reduced (P < 0.001), the P4 concentration was significantly increased (P = 0.003), and the concentrations of FSH, T and AND had no difference in the follicles of Gn-stimulated cycle. Cell cycle– and meiosis-associated genes were down-regulated by Gns stimulation, whereas immune- and cytokine-associated genes were up-regulated. Hormone levels were also affected by Gns stimulation. Compared with natural-cycle follicles,putative markers associated with oocyte quality and follicle maturation were significantly different from those in Gn-stimulated follicles. Hormone levels in follicles were compatible with the steroidogenic patterns of granulosa cell, which reflects the follicle maturation and oocyte quality.

The dynamic transcriptional regulation and interactions of human germlines and surrounding somatic cells during folliculogenesis remain unknown. Using RNA sequencing (RNA-seq) analysis of human oocytes and corresponding granulosa cells (GCs) spanning five follicular stages, we revealed unique features in transcriptional machinery, transcription factor networks, and reciprocal interactions in human oocytes and GCs that displayed developmental- stage-specific expression patterns. Notably, we identified specific gene signatures of two cell types in particular developmental stage that may reflect developmental competency and ovarian reserve. Additionally, we uncovered key pathways that may concert germline-somatic interactions and drive the transition of primordial-to-primary follicle, which represents follicle activation. Thus, our work provides key insights into the crucial features of the transcriptional regulation in the stepwise folliculogenesis and offers important clues for improving follicle recruitment in vivo and restoring fully competent oocytes in vitro.

In vitro maturation (IVM), the maturation in culture of immature oocytes, has been used in clinic for more than 20 years. Although IVM has the specific advantages of low cost and minor side effects over controlled ovarian stimulation, the prevalence of IVM is less than 1% of routine in vitro fertilization and embryo transfer techniques in many reproductive centers. In this review, we searched the MEDLINE database for all full texts and/or abstract articles published in English with content related to oocyte IVM mainly between 2000 and 2016. Many different aspects of the IVM method may influence oocyte potential, including priming, gonadotrophin, growth factors, and culture times. The culture conditions of IVM result in alterations in the oocyte or cumulus cell transcriptome that are not observed under in vivo culture conditions. Additionally, epigenetic modifications, such as DNA methylation or acetylation, are also different between in vitro and in vivo cultured oocytes. In sum, current IVM technique is still not popular and requires more systematic and intensive research to improve its effects and applications. This review will help point our problems, supply evidence or clues for future improving IVM technique, thus assist patients for fertility treatment or preservation as an additional option.

Objective To investigate the effect of vitrification on the development potential and transcriptome of in vitro matured human oocytes. Methods This is a prospective cohort study. The infertility patients treated by laparoscopic surgery combined with in vitro maturation (IVM) treatment were analyzed in Center for Reproductive Medicine of Peking University Third Hospital, between September 2014 and March 2016. The research subjects were divided into two groups: IVM group (group A, n=13) and IVM-vitrification group (group B, n=24). The early embryonic development and transcriptome at the single cell level of the oocytes from two groups were compared and analyzed. Results The process of oocytes vitrification-thawing after IVM had no significant effect on the early embryonic development. There was no significant difference in survival oocyte fertilization rate, cleavage rate, advanced embryo rate and transferable embryo rate between the two groups. However, vitrification-thawing after IVM had a certain effect on transcriptome. Compared with group A, 1 913 genes in group B showed differential expression, of which 570 genes were upregulated and mainly enriched to 59 biological processes while 1 343 genes were downregulated and mainly enriched to 140 biological processes. Furthermore, some differentially expressed genes and their related biological processes were involved in the regulation of oocyte quality, fertilization and embryonic development potential. Conclusion The process of oocyte vitrification-thawing after IVM had no significant effect on early embryonic development, but had some effects on transcriptome. These changed genes were related to oocyte quality, fertilization and embryo development potential, suggesting that vitrification-thawing may affect the offspring safety. Key words: In vitro maturation (IVM); Oocyte; Vitrification; Early embryonic development; Transcriptome

Management of women with reduced ovarian reserve or poor ovarian response (POR) to stimulation is one of the major challenges in reproductive medicine. The primary causes of POR remain elusive and oxidative stress was proposed as one of the important contributors. It has been suggested that focus on the specific subpopulations within heterogeneous group of poor responders could assist in evaluating optimal management strategies for these patients. This study investigated the effect of anti-oxidant treatment with coenzyme Q10 (CoQ10) on ovarian response and embryo quality in young low-prognosis patients with POR.

Folliculogenesis is a highly regulated process that involves bidirectional interactions of the oocytes and surrounding granulosa cells (GCs). Little is unknown, however, about the transcriptomic profiles of human oocytes and GCs throughout folliculogenesis. Here we performed a high resolution RNA-Seq of human oocytes and GCs at each follicular stage, which revealed unique transcriptional profiles, stage-specific signature genes, oocyte- and GC-derived genes that reflect ovarian reserve. We identified reciprocal cell-to-cell interactions between oocytes and GCs, including NOTCH, TGF-β signaling and gap junctions and determined the expression patterns of maternal-effect genes involved in folliculogenesis and early embryogenesis. Finally, we demonstrated robust differences between human and mice oocyte transcriptomes. This is the first comprehensive overview of the transcriptomic signatures governing the stepwise human folliculogenesis in-vivo that provides a valuable resource for basic and translational research in human reproductive biology.

Few studies have evaluated Hedgehog (Hh) signaling pathway activation in different types of ovarian tumors including benign, borderline and malignant ovarian tumors. The present study investigated the expression of Hh signaling pathway components (SHH, SMO, PTCH, and GLI1) in 193 ovarian epithelial tumor specimens (including 147 malignant epithelial ovarian cancers, 30 borderline ovarian tumors, 16 benign ovarian epithelial tumors) and 11 normal ovarian epithelial tissues by immunohistochemistry. The results demonstrated widespread expression of Hh pathway molecules in ovarian tumors. However, there was no significant difference in the expression intensity of SHH among the four groups (P>0.05). Statistically significant differences were identified in the expression intensity of the SMO, PICH and GLI1 among groups (P<0.001). In addition, significant differences were also revealed in the expression levels of SMO (P=0.013) and GLI1 (P=0.0005) between the platinum drug-sensitive and drug-resistant groups. The overexpression of SMO and GLI1 was further confirmed in the cisplatin-resistant ovarian cancer cell line A2780/DDP by immunofluorescence, flow cytometry and western blotting. The results revealed that the Hh pathway components SMO, PICH and GLI1 are activated in ovarian epithelial tumors. Novel potential associations between cisplatin resistance and the overexpression of SMO and Gli1 in malignant epithelial ovarian cancer were also observed, which may provide an innovative approach to the treatment of drug resistant ovarian epithelial cancer.

In an attempt to explore the early developmental arrest in embryos from polycystic ovarian syndrome (PCOS) patients, we sequenced the transcriptome profiles of PCOS arrested 2-cell embryos, non-PCOS arrested 2-cell embryos and non-arrested 2-cell embryos using single-cell RNA-Seq technique. Differential expression analysis was performed using the DEGSeq R package. Gene Ontology (GO) enrichment was analyzed using the GOseq R package. Data revealed 62 differentially expressed genes between non-PCOS arrested and PCOS arrested embryos and 2217 differentially expressed genes between PCOS arrested and non-arrested 2-cell embryos. A total of 49 differently expressed genes (DEGs) were annotated with GO terms in the up-regulated genes between PCOS arrested and non-PCOS arrested embryos after GO enrichment. A total of 29 DEGs were annotated with GO terms in the down-regulated genes between PCOS arrested and non-arrested 2-cell embryos after GO enrichment. These data can provide a reference for screening specific genes involved in the arrest of PCOS embryos.

The aim of this study was to investigate the relationship between normal Fragile X mental retardation gene 1 (FMR1) CGG repeat numbers and primary ovarian insufficiency (POI) occurrence or subsequent resumption of ovarian function. A total of 122 women with POI and 105 controls were followed up and analysed in our centre. The prevalence of premutation and intermediate range of FMR1 CGG repeats in Han Chinese women with POI was only 0.81% (1/122) and 1.64% (2/122), respectively. The risk of POI occurrence for less than 26 CGG repeats and 29 or more CGG repeats in allele1 (smaller allele) was significantly higher than that for 26-28 CGG repeats (odds ratio 13.50, 95% confidence interval: 3.21 to 56.77 and 6.32, 95% confidence interval: 2.49 to 16.09 respectively; both P < 0.001). No significant difference was found in the CGG repeat distribution (<26, 26-28, or ≥29) in FMR1 allele1 between POI cases whose ovarian function resumed and those whose ovarian function did not. It is suggested that the CGG repeat number in allele1, but not that in allele2 (longer allele), was significantly associated with POI occurrence (P < 0.001). Fewer than 26 or more than 28 CGG repeats in FMR1 allele1 were both risk factors of POI occurrence.

The incidence of ectopic pregnancy after assisted reproductive technology is increased approximately 2.5-5-fold compared with natural conceptions.Strategies were used to decrease the incidence of ectopic pregnancy, but ectopic pregnancy still occurs. In the present study, women were selected with decreased ovarian reserve (defined as FSH > 10 IU/L) aged 20 to 38 years who underwent IVF-ET between 2009 and 2014. These 2,061 women were age-matched with an equal number of women with normal ovarian reserve (defined as FSH ≤ 10 IU/L). During cycles following fresh embryo transfer, 93 patients were diagnosed with ectopic pregnancy. The incidence of ectopic pregnancy in clinical pregnancies was significantly higher in the decreased ovarian reserve than in the normal ovarian reserve group (5.51% vs. 2.99%). After adjusting for confounding factors, the incidence of ectopic pregnancy was significantly associated with decreased ovarian reserve. Our results showed that decreased ovarian reserve is an independent risk factor for ectopic pregnancy after in vitro fertilization-embryo transfer.

Objective To observe the changes and effects of laparoscopic ovarian drilling (LOD) combined with transvaginal immature follicle aspiration (IMFA) on patients with refractory polycystic ovary syndrome (PCOS).Methods A total of 124 patients with refractory PCOS from September 2014 to July 2016 were recruited in this study.According to patients' consents prior to the surgery, 83 patients who preferred to receive ultrasound guided IMFA followed by LOD were enrolled in LOD+IMFA group, while 41 patients who refused to take IMFA were recruited into the LOD group, receiving laparoscopy and ovarian drilling only.Serum hormone levels, including luteinizing hormone (LH), androstenedione (A), free androgen index (FAI) and anti-mullerian hormone (AMH), were evaluated before surgeries.In the following 6-12 months, spontaneous resumption of menstruation, ovulation-stimulation treatment effects, and pregnancy rates were monitored in the two groups.Results Serum levels of LH, A, AMH in both groups were decreased significantly after surgeries compared to the levels before surgeries(P<0.05), and no significant differences were found between the two groups(P>0.05).There was no significant difference in the rates of resumption of menstruation between the two groups [39.8% (33/83) in LOD+IMFA group, and 34.1% (14/41) in LOD group, respectively, χ2=0.367, P=0.544].However, after ovulation induction treatment, the ovulation rate in LOD+IMFA group [78.0% (39/50)] was significantly higher than that in LOD group [37.0% (10/27), χ2=12.713, P=0.000].The pregnancy rate had no significant difference between the two groups [44.6% (29/65) vs.32.3% (10/31), χ2=1.329, P=0.249].In LOD+IMFA group, 98.8% (82/83) patients acquired mature oocytes.Conclusions LOD+IMFA treatment for refractory PCOS is safe and efficient.The immature oocytes obtained in the surgery can be stored for patients' fertility preservation.

STUDY QUESTION What is the effect of human ovarian tissue cryopreservation on single follicular development in vitro? SUMMARY ANSWER Vitrification had a greater negative effect on growth and gene expression of human ovarian follicles when compared with fresh follicles. WHAT IS KNOWN ALREADY For human ovarian cortex cryopreservation, the conventional option is slow freezing while more recently vitrification has been demonstrated to maintain good quality and function of ovarian tissues. STUDY DESIGN, SIZE, DURATION Ovarian tissues were collected from 11 patients. For every patient, the ovarian cortex was divided into three samples: Fresh, slow-rate freezing (Slow) and vitrification (Vit). Tissue histology was performed and follicles were isolated for single-cell mRNA analysis and in vitro culture (IVC) in 1% alginate for 8 days. PARTICIPANTS/MATERIALS, SETTING, METHODS Follicle morphology was assessed with hematoxylin-eosin analysis. Follicles were individually embedded in alginate (1% w/v) and cultured in vitro for 8 days. Follicle survival and growth were assessed by microscopy. Follicle viability was observed after Calcein-AM and ethidium homodimer-I (Ca-AM/EthD-I) staining. Expression of genes, including GDF9 (growth differentiation factor 9), BMP15 (bone morphogenetic protein 15) and ZP3 (zona pellucida glycoprotein 3) in oocytes and AMH (anti-Mullerian hormone), FSHR (FSH receptor), CYP11A (cholesterol side-chain cleavage cytochrome P450) and STAR (steroidogenic acute regulatory protein) in GCs, was evaluated by single-cell mRNA analysis. MAIN RESULTS AND THE ROLE OF CHANCE A total of 129 follicles were separated from ovarian cortex (Fresh n = 44; Slow n = 40; Vit n = 45). The percentage of damaged oocytes and granulosa cells was significantly higher in both the Slow and Vit groups, as compared with Fresh control (P< 0.05). The growth of follicles in vitro was significantly delayed in the Vit group compared with the Fresh group (P< 0.05). Both slow freezing (P< 0.05) and vitrification (P< 0.05) down-regulated the mRNA levels of ZP3 and CYP11A compared with Fresh group, while there was no significant difference between the Slow and Vit groups (P> 0.05). Vitrification also down-regulates AMH mRNA levels compared with Fresh group (P< 0.05). LIMITATIONS, REASONS FOR CAUTION Only short-term IVC studies (8 days) are reported. Further study should be performed to examine and improve follicular development in a long-term culture system after cryopreservation. WIDER IMPLICATIONS OF THE FINDINGS This is the first comparison of gene expression and growth of single human ovarian follicles in vitro after either slow freezing or vitrification. With the decreased gene expression and growth during IVC, damage by cryopreservation still exists and needs to be minimized during the long-term IVC of follicles in the future for eventual clinical application. STUDY FUNDING/COMPETING INTERESTS This work was supported by the National Natural Science Foundation of China (31230047, 81571386, 81471508, 31429004 and 81501247), National Natural Science Foundation of Beijing (7142166) and Mega-projects of Science Research for the 12th five-year plan (2012ba132b05). There are no conflicts of interest to declare.

Primary ovarian insufficiency (POI), also known as premature ovarian failure (POF), is defined as more than six months of cessation of menses before the age of 40 years, with two serum follicle stimulating hormone (FSH) levels (at least 1 month apart) falling in the menopause range. The cause of POI remains undetermined in the majority of cases, although some studies have reported increased levels of reactive oxygen species (ROS) in idiopathic POF. The role of mitochondrial DNA in the pathogenesis of POI has not been studied extensively. This aim of this study was to uncover underlying mitochondrial genetic defects in patients with POI. The entire region of the mitochondrial genome was amplified in subjects with idiopathic POI (n=63) and age-matched healthy female controls (n=63) using nine pair sets of primers, followed by screening of the mitochondrial genome using an Illumina MiSeq. We identified a total of 96 non-synonymous mitochondrial variations in POI patients and 93 non-synonymous variations in control subjects. Of these, 21 (9 in POI and 12 in control) non-synonymous variations had not been reported previously. Eight mitochondrial cytochrome coxidase 1 (MT-CO1) missense variants were identified in POI patients, whereas only four missense mutations were observed in controls. A high incidence of MT-CO1 missense variants were identified in POI patients compared with controls, and the difference between the groups was statistically significant (13/63 vs. 5/63, p=0.042). Our results show that patients with primary ovarian insufficiency exhibit an increased incidence of mitochondrial cytochrome c oxidase 1 gene mutations, suggesting that MT-CO1 gene mutation may be causal in POI.

Preimplantation genetic diagnosis (PGD) gives couples who have a high risk of transmitting genetic disorders to their baby the chance to have a healthy offspring through embryo genetic analysis and selection. Preimplantation genetic screening (PGS) is an effective method to select euploid embryos that may prevent repeated implantation failure or miscarriage. However, how and to whom PGS should be provided is a controversial topic. The first successful case of PGD of a human being was reported in 1990, and there have been tremendous improvements in this technology since then. Both embryo biopsy and genetic technologies have been improved dramatically, which increase the accuracy and expand the indications of PGD/PGS.

Y-chromosome microdeletions (YCMs) have been found at a much higher rate in infertile men than fertile controls. A specific deletion in the azoospermia factor locus (AZF) at Yq11 is significantly associated with male infertility. Whether assisted reproductive technology (ART) increases the risk of YCM in ART-derived offspring remains unclear. In this study the occurrence of YCM in 199 fathers and their 228 sons (Chinese, Han ethnicity), including 85 offspring conceived by IVF, 73 by intra-cytoplasmic sperm injection (ICSI) and 70 by natural conception, was investigated. Nineteen candidate genes related to YCM were analysed by multiplex ligation-dependent probe amplification. We identified one de novo YCM from 70 naturally-conceived offspring and none from 158 ART-conceived offspring and found no statistical significance between these two groups. There was no statistically-significant difference in the detection rate of the father’s Y-chromosome microdeletion group: IVF 10.7% (8/75), ICSI 3.2% (2/63), natural conception 8.2% (5/61). These results suggest that ART does not increase the risk of YCM in male offspring.

Gonadotropins have been widely used in human-assisted reproduction and animal science for the past four decades. However, the effects of gonadotropins on oocyte maturation at the molecular and biochemical levels are poorly understood. To determine the effects of gonadotropins (recombinant follicle stimulating hormone and urinary human menopausal gonadotropin) on oocyte maturation, we used the bovine oocyte in vitro maturation model. First, we studied the effects of increasing gonadotropin concentrations on nuclear maturation and mitochondrial function in oocytes. Gonadotropins at concentrations of 0.075 and 0.75 IU/ml improved nuclear maturation and increased inner mitochondrial membrane potential and ATP levels; however, there were no beneficial effects at concentrations of 7.5 and 75 IU/ml. Second, we studied the effects of increasing gonadotropin concentrations on the status of methylation in matured (MII) oocytes. Aberrant methylation and demethylation of H19, SNRPN, and PEG3 genes were observed in MII oocytes at all concentrations except 0.075 IU/ml. The expression of genes that function in spindle formation, cell cycle control, and methylation was also downregulated by high gonadotropin concentrations. In conclusion, we established the optimal gonadotropin concentration (i.e., 0.075 IU/ml) to be used for bovine oocyte in vitro maturation studies. These results may provide a guide for clinical stimulation protocols and help to reduce the risks associated with gonadotropin administration during in vitro fertilization treatment.